1. Field of the Invention
The present invention relates to a method used in a wireless communication system and related communication device, and more particularly, to a method of jointly encoding channel state information (CSI) reports and hybrid automatic repeat request (HARQ) feedbacks in a wireless communication system and related communication device.
2. Description of the Prior Art
A long-term evolution (LTE) system, initiated by the third generation partnership project (3GPP), is now being regarded as a new radio interface and radio network architecture that provides a high data rate, low latency, packet optimization, and improved system capacity and coverage. In the LTE system, a radio access network known as an evolved universal terrestrial radio access network (E-UTRAN) includes a plurality of evolved Node-Bs (eNBs) for communicating with a plurality of user equipments (UEs) and communicates with a core network including a mobility management entity (MME), serving gateway, etc for NAS (Non Access Stratum) control.
An LTE-advanced (LTE-A) system, as its name implies, is an evolution of the LTE system. The LTE-A system targets faster switching between power states, improves performance at the coverage edge of an eNB, and includes advanced techniques, such as carrier aggregation (CA), coordinated multipoint transmission/reception (COMP), uplink (UL) multiple-input multiple-output (MIMO), etc. For a UE and an eNB to communicate with each other in the LTE-A system, the UE and the eNB must support standards developed for the LTE-A system, such as the 3GPP Rel-10 standard or later versions.
In the LTE-A system, since a UE may be served by multiple cells, the UE may need to report Hybrid Automatic Repeat Request (HARQ) acknowledgement/negative acknowledgements (ACKs/NACKs) to each cell at the same time. In the prior art, a physical uplink control channel (PUCCH) format 3 including 48 bits is defined to convey the HARQ ACKs/NACKs for advanced techniques such as CA. Please refer to FIG. 1, which is a schematic diagram of a conventional process 10 for encoding HARQ ACKs/NACKs in the CA technology when the total number of HARQ ACK/NACK bits NA/NPUCCH format 3 is less than 11 (i.e., NA/NPUCCH format 3≦11) As shown in FIG. 1, the HARQ ACKs/NACK bits a0, a1, a2, . . . , aNA/NPUCCH format 3−1 (denoted by an) are encoded into a data stream {tilde over (b)}0, {tilde over (b)}1, {tilde over (b)}2, . . . , {tilde over (b)}31 (denoted by {tilde over (b)}i) through a Reed-Muller code RM(32, O) first (step 100), wherein O is the number of input bits,
                    b        ~            i        =                  ∑                  n          =          0                                      N                          A              /              N                                      PUCCH              ⁢                                                          ⁢              format              ⁢                                                          ⁢              3                                -          1                    ⁢                          ⁢                        (                                    a              n                        ·                          M                              i                ,                n                                              )                ⁢        mod        ⁢                                  ⁢        2              ,i=0, 1, 2, . . . , 31, and the basis sequences Mi,n are defined in Table 1. Then, an output data stream b0, b1, b2, . . . , bB-1 (denoted by b1) is obtained by circular repetition of the data stream {tilde over (b)}0, {tilde over (b)}1, {tilde over (b)}2, . . . , {tilde over (b)}31 i.e., bj={tilde over (b)}(i mod 32) (step 102), wherein j=0, 1, 2, . . . , B-1, B is the bandwidth for transmitting the HARQ ACKs/NACKs. Please continue referring to FIG. 2, which is a schematic diagram of a conventional process 20 for encoding HARQ ACKs/NACKs in the CA technology when the total number of HARQ ACK/NACK bits NA/NPUCCH format 3 equals a number between 11 and 21 (i.e., 11<NA/NPUCCH format 3≦21) As shown in FIG. 2, the HARQ ACKs/NACK bits a0, a1, a2, . . . , aNA/NPUCCH format 3−1 (denoted by an) are de-multiplexed into two data streams a0, a1, a2, . . . , a┌NA/NPUCCH format 3/2┐−1 (denoted by ãm) and a┌NA/NPUCCH format 3/2┐, a┌NA/NPUCCH format 3/2┐+1, a┌NA/NPUCCH format 3/2┐+2, . . . , a┌NA/NPUCCH format 3/2┐−1, (denoted by {tilde over (ã)}1) first (step 200). Then, the data streams a0, a1, a2, . . . , a┌NA/NPUCCH format 3/2┐−1 and a┌NA/NPUCCH format 3/2┐, a┌NA/NPUCCH format 3/2┐+1, a┌NA/NPUCCH format 3/2┐+2, . . . , aNA/NPUCCH format 3−1, are encoded through the Reed-Muller code RM(32, O) (steps 202, 204) and truncated to 24 bits (steps 206, 208) to obtain data streams {tilde over (b)}i and {tilde over ({tilde over (b)}i, respectively, wherein
                    b        ~            i        =                  ∑                  n          =          0                                      ⌈                          N                              A                /                N                                            PUCCH                ⁢                                                                  ⁢                format                ⁢                                                                  ⁢                                  3                                      /                    2                                                                        ⌉                    -          1                    ⁢                          ⁢                        (                                    a              n                        ·                          M                              i                ,                n                                              )                ⁢        mod        ⁢                                  ⁢        2              ,
                    b        ≈            i        =                  ∑                  n          =          0                                      N                          A              /              N                                      PUCCH              ⁢                                                          ⁢              format              ⁢                                                          ⁢              3                                -                      ⌈                          N                              A                /                N                                            PUCCH                ⁢                                                                  ⁢                format                ⁢                                                                  ⁢                                  3                                      /                    2                                                                        ⌉                    -          1                    ⁢                          ⁢                        (                                    a                                                ⌈                                      N                                          A                      /                      N                                                              PUCCH                      ⁢                                                                                          ⁢                      format                      ⁢                                                                                          ⁢                                              3                                                  /                          2                                                                                                      ⌉                                                  +                  n                                                      ·                          M                              i                ,                n                                              )                ⁢        mod        ⁢                                  ⁢        2              ,i=0, 1, 2, . . . , 23, and the basis sequences Mi,n are defined in Table 1. Finally, an output data stream b0, b1, b2, . . . , bB-I (denoted by b1) is obtained by the alternate concatenation of the bit sequences {tilde over (b)}0, {tilde over (b)}1, {tilde over (b)}2, . . . , {tilde over (b)}23 and {tilde over ({tilde over (b)}0, {tilde over ({tilde over (b)}1, {tilde over ({tilde over (b)}2, . . . , {tilde over ({tilde over (b)}23 (step 210) as the following pseudo-code:
Set i, j = 0while i < B  bi = {tilde over (b)}j , bi+1 = {tilde over (b)}j+1 , bi+2 =   , bi+3 =    i = i + 4, j = j + 2end while
Therefore, in the conventional processes 10 and 20, the maximum number of ACK/NACK bits that can be transmitted in the PUCCH format 3 is 10 for frequency division duplex (FDD), and the maximum number of ACK/NACK bits that can be transmitted in the PUCCH format 3 is 20 for time division duplex (TDD). However, it is not enough for certain advanced applications.
TABLE 1iMi,0Mi,1Mi,2Mi,3Mi,4Mi,5Mi,6Mi,7Mi,8Mi,9Mi,100110000000011111000000112100100101113101100001014111100010015110010111016101010101117100110011018110110010119101110100111010100111011111110011010112100101011111311010101011141000110100115110011110111611101110010171001110010018110111110001910000110000201010001000121110100000112210001001101231110100011124111110111102511000111001261011010011027111101011102810101110100291011111110030111111111113110000000000
Channel state information (CSI) includes channel quality indicator (CQI), precoding matrix indicator (PMI), precoding type indicator (PTI), and/or rank indication (RI). CSI reports are classified into 10 types, 1, 1a, 2, 2a, 2b, 2c, 3, 4, 5, and 6, each type reporting different contents. For example, Type 2 report supports wideband CQI and PMI feedback, and Type 3 report supports RI feedback. When multiple CSI reports for different cells need to be transmitted simultaneously, the 3GPP Rel-10 standard requires the UE to drop reports with lower priorities and to deliver only one CSI report at one time.
In detail, if the UE is configured with more than one serving cell (e.g., the UE and the eNB support CA), the UE transmits a CSI report of only one serving cell in any given subframe. For a given subframe, if a CSI report with PUCCH reporting type 3, 5, 6, or 2a of one serving cell collides with a CSI report with PUCCH reporting type 1, 1a, 2, 2b, 2c, or 4 of another serving cell, the latter CSI with PUCCH reporting type 1, 1a, 2, 2b, 2c, or 4 having lower priority may be dropped. For a given subframe, if a CSI report with PUCCH reporting type 2, 2b, 2c, or 4 of one serving cell collides with a CSI report with PUCCH reporting type 1 or 1a of another serving cell, the latter CSI report with PUCCH reporting type 1, or 1a having lower priority may be dropped.
For a given subframe, if collision among CSI reports of different serving cells with PUCCH reporting type of the same priority occurs, the CSI of the serving cell with lowest serving cell index is reported, and CSI of all other serving cells are dropped.
For a wireless communication system supporting CoMP transmission/reception, a cell may correspond to multiple transmission points (TPs). In case of collision among CSI reports of different TPs corresponding to the same serving cells with PUCCH reporting type of the same priority, the priorities of the CSI reports may be the same according to the prior art. Since the benefit of the CoMP technology originates from coordination among TPs, it is inappropriate to deliver only one CSI report at one time.
Thus, how to deliver more HARQ bits and multiple CSI reports at one time is a topic to be addressed and discussed.